The present invention is directed to an improved method for the production of composite articles by pultrusion.
It has long been known to produce composite reinforced articles such as prepreg tapes and rovings by various pultrusion methods. See, for example, U.S. Pat. Nos. 3,042,570; 3,608,033; 3,684,622; 3,742,107; 3,793,108; 3,960,629; 3,993,726; 4,132,756; and 4,312,917. While such methods are generally capable of producing acceptable products, it is desirable in certain instances to employ a matrix material which enhances the ability of the product to be employed in certain environments where thermal and chemical stability are important. High degrees of orientation of the polymer matrix are also sometimes desirable to optimize the mechanical properties of the product.
It is further necessary that articles produced by pultrusion satisfy the following basic requirements during processing: (1) that the reinforcing fibers be uniformly distributed throughout the polymer matrix material; (2) that the bundles of the reinforcing fibers which are employed should be well impregnated with the matrix polymer; and (3) that the fibers should be sufficiently bonded to the matrix polymer.